An image-forming method for developing electrostatic latent images is employed in copiers, multifunction printers, and printers. Such an image-forming method generally includes forming an electrostatic latent image on a photoreceptor, developing the electrostatic latent image using toner to form a toner image, transferring the toner image to a transfer material such as paper, and fixing the toner image to the transfer material by a heat-and-pressure fixing method to form a fixed image.
Various methods for fixing a toner image to a transfer material such as paper have been developed. Examples of such methods include a hot-roller fixing method of fixing a toner image to a transfer material using a hot roller and a pressure roller and a film fixing method of fixing a toner image to a transfer material by bringing a heating element and a pressure member into contact using a film interposed therebetween.
In these fixing methods, the surface of the hot roller or film and the toner image on the transfer material are brought into contact with each other. Consequently, the thermal efficiency with which the toner image is fused to the transfer material is high, which leads to quick fixing. Therefore, these fixing methods are widely employed in multifunction printers and printers.
However, in the fixing methods, some toner may adhere to the surface of the fixing member because the surface of the hot roller or the fixing member such as a film and the toner are brought into contact with each other when the toner is fused. As a result, an offset phenomenon, i.e., retransfer of the toner adhered to the hot roller or film to the next transfer material, may occur. In order to address such a problem, a toner that contains a wax such as paraffin or low-molecular-weight polyolefin in the toner particles so as to suppress the adhesion of the toner to the fixing member has been proposed (see PTL 1). In order to maintain the release effect of wax even when a fixing temperature is in low-temperature range and in high-temperature range, a toner that contains both a low-melting point wax and high-melting point wax has been proposed (see PTL 2). As a result, the occurrence of the toner offset to a fixing member was reduced and the stable fixability of toner over broad temperature range was achieved.